Binding Energy Of NO Research Articles

Catalytic decomposition of NO using molten gallium: an experimental and computational study

Molten gallium (Ga) catalyzes the direct decomposition of NO. In a bubble column reactor, NO decomposition was conducted by injecting NO-containing bubbles into molten Ga at elevated temperatures (> 400 °C), and > 90% conversion was achieved in only ∼ 0.2 s of residence time at 550 °C. Computational analysis showed that despite the weak binding energy of NO to Ga surface (34.4 kJ/mol), thermodynamically favored NO* dissociation on Ga (−138.3 kJ/mol) facilitated decomposition. Although Ga surfaces can be poisoned by O* generated by the dissociation of NO*, introducing reduction gas promoted OH* formation (−51.1 kJ/mol) on the surface and subsequent H2O desorption, and consequently reactivated the Ga surface. NO decomposition and catalyst regeneration using reducing gas was repeated over 15 cycles in a single droplet reactor, and NO conversion was stably maintained. Experimental and computational results support the potential use of molten Ga as a catalyst for the direct decomposition of NO.

Quantum chemical study of the structure, spectroscopy and reactivity of NO+.(H2O) n=1-5 clusters.

Quantum chemical methods including Møller-Plesset perturbation (MP2) theory and density functional theory (DFT) have been used to study the structure, spectroscopy and reactivity of NO+(H2O) n=1-5 clusters. MP2/6-311++G** calculations are shown to describe the structure and spectroscopy of the clusters well. DFT calculations with exchange-correlation functionals with a low fraction of Hartree-Fock exchange give a binding energy of NO+(H2O) that is too high and incorrectly predict the lowest energy structure of NO+(H2O)2, and this error may be associated with a delocalization of charge onto the water molecule directly binding to NO+ Ab initio molecular dynamics (AIMD) simulations were performed to study the NO+(H2O)5 [Formula: see text] H+(H2O)4 + HONO reaction to investigate the formation of HONO from NO+(H2O)5 Whether an intracluster reaction to form HONO is observed depends on the level of electronic structure theory used. Of note is that methods that accurately describe the relative energies of the product and reactant clusters did not show reactions on the timescales studied. This suggests that in the upper atmosphere the reaction may occur owing to the energy present in the NO+(H2O)5 complex following its formation.This article is part of the theme issue 'Modern theoretical chemistry'.

The binding energies of NO–Rg (Rg = He, Ne, Ar) determined by velocity map imaging

We report velocity map imaging measurements of the binding energies, D(0), of NO-Rg (Rg = He, Ne, Ar) complexes. The X state binding energies determined are 3.0 ± 1.8, 28.6 ± 1.7, and 93.5 ± 0.9 cm(-1) for NO-He, -Ne, and -Ar, respectively. These values compare reasonably well with ab initio calculations. Because the Ã-X transitions were unable to be observed for NO-He and NO-Ne, values for the binding energies in the à state of these complexes have not been determined. Based on our X state value and the reported Ã-X origin band position, the à state binding energy for NO-Ar was determined to be 50.6 ± 0.9 cm(-1).

CO/NO and CO/NO/O 2 reactions over a Au–Pd single crystal catalyst

NO reduction by CO was investigated over a AuPd(1 0 0) model catalyst at near atmospheric pressures. The alloy catalyst exhibits higher CO 2 formation rates below ∼550 K than does pure Pd, although the binding energy of NO on the alloy surface is substantially less, i.e., its dissociation tendency is much less, compared with pure Pd. This behavior is rationalized by the fact that the low CO/NO-binding energies with the alloy surface provide a substantial population of empty ensembles for NO dissociation at relatively low temperatures. Moreover, AuPd(1 0 0) catalyzes the CO + NO reaction with much higher N 2 selectivity than does pure Pd. Reaction kinetics data reveal that contiguous Pd sites are essential for NO dissociation. The reaction orders in CO and NO pressures, vastly different from Pd and Rh, are also a consequence of the low-binding energies of CO and NO on the alloy surface. It is also found that low-pressure NO promotes the CO + O 2 reaction via gas-phase NO 2 formation; the latter dissociates to form O (ads) more efficiently than does O 2 below ∼600 K. However, when the NO pressure exceeds a critical value, gas-phase NO 2 causes surface oxidation and thus inhibits CO 2 formation. The current study suggests that AuPd alloys should be superior catalysts compared to traditional catalysts with respect to the “cold start” problem in catalytic automobile pollutant removal.

The Adsorption of NO on Various Metal Tape-Porphyrins: A First-Principles Study

The adsorption of NO on various metal tape-porphyrins (Mn, Fe, and Co) is studied using first-principles calculations based on density functional theory (DFT). In this work we discuss the geometric structure and electronic properties of metal tape-porphyrins and the effect of the adsorption of NO on their properties. The results show that metal atoms protrude from the porphyrin plane toward the NO molecule. At the stable position, the variation of the metal–N–O angle is in the order: Co–N–O (123°) < Fe–N–O (148°) < Mn–N–O (180°). The N–O bond length in the metal tape-porphyrins is slightly longer than that of the isolated NO molecule. These results are consistent with other DFT calculations and experimental results. We also found that the binding energy of NO with metal porphyrins increases in the order CoTP–NO (1.718 eV) < FeTP–NO (1.719 eV) < MnTP–NO (1.736 eV). As regards the electronic properties, there is a metal–insulator transition in FeTP–NO. For CoTP–NO and MnTP–NO, we found that CoTP shows insul...

Ferric and Ferrous Iron in Nitroso‐Myoglobin: Computer Simulations of Stable and Metastable States and Their Infrared Spectra

The binding of NO to iron is involved in the biological function of many heme proteins. Contrary to ligands like CO and O(2), which only bind to ferrous (Fe(II)) iron, NO binds to both ferrous and ferric (Fe(III)) iron. In a particular protein, the natural oxidation state can therefore be expected to be tailored to the required function. Herein, we present an ab initio potential-energy surface for ferric iron interacting with NO. This potential-energy surface exhibits three minima corresponding to eta(1)-NO coordination (the global minimum), eta(1)-ON coordination and eta(2) coordination. This contrasts with the potential-energy surface for Fe(II)-NO, which exhibits only two minima (the eta(2) coordination mode for Fe(II) is a transition state, not a minimum). In addition, the binding energies of NO are substantially larger for Fe(III) than for Fe(II). We have performed molecular dynamics simulations for NO bound to ferric myoglobin (Mb(III)) and compare these with results obtained for Mb(II). Over the duration of our simulations (1.5 ns), all three binding modes are found to be stable at 200 K and transiently stable at 300 K, with eventual transformation to the eta(1)-NO global-minimum conformation. We discuss the implication of these results related to studies of rebinding processes in myoglobin.

Potential energy curves along the diffusion paths of NO on the small-sized Cu(100) model cluster

Hybrid density functional theory (DFT) calculations have been carried out for the nitric oxide NO molecule on the Cu model cluster in order to shed light on the diffusion mechanism of the NO molecule on the Cu(100) cluster model surface. The metal surface was represented approximately by a finite metal cluster Cu 9. Three binding sites, ‘two-fold site’, ‘four-fold site’, and ‘on-top site’, were considered in the present study. In two-fold site, NO binds to two Cu atoms in the shorter Cu–Cu bond of the surface, whereas NO in four-fold site was bound in the longer Cu–Cu bond and interacts with four Cu atoms. The binding energies of NO were larger in the order, on-top<two-fold<four-fold sites. Also, it was found that on-top site is transition state for the diffusion of NO. The activation energy along the diffusion path from two-fold site to next neighboring two-fold site via on-top site was calculated to be 4.8 kcal/mol, while the diffusion was a symmetry-allowed adiabatic process. On the other hand, the barrier height for the diffusion path from four-fold site to four-fold site was as high as 8.90 kcal/mol, and the diffusion needs non-adiabatic process (symmetry-forbidden). The mechanism of the adsorption of NO on Cu was discussed on the basis of theoretical results.

A mass spectrometric and computational study of gaseous peroxynitric acid and (HOONO 2)H + protomers

The positive ion chemistry of peroxynitric acid ( 1) was investigated in the gas phase by mass-analyzed ion kinetic, collisionally activated dissociation, and Fourier transform-ion cyclotron resonance mass spectrometric techniques and theoretical methods up to the B3LYP/6-311++g(3 df,2 pd) and G2, i.e. QCISD(T)/6-311+g(3 df,2 pd), levels. The ion–neutral complex HOOH–NO 2 + ( 1a) is the only detectable protomer in CI experiments involving the protonation of 1 by H 3O +, and can also be obtained from the reaction of NO 2 + with H 2O 2. 1a behaves as a protonating and nitrating agent toward gaseous nucleophiles. The experimental proton affinity of 1 is estimated to be 176 ± 3 kcal mol −1, in excellent agreement with the 175 ± 2 kcal mol −1 G2 PA. The theoretical results show that 1a is more stable than the HOONO 2H + ( 1b) and the H 2OONO 2 + ( 1c) protomers by 13 and 16 kcal mol −1, respectively, at the B3LYP level of theory, and account for the exclusive formation of 1a in the CI experiments. The experimental and B3LYP theoretical binding energy of NO 2 + to H 2O 2 amounts to 18 ± 2 kcal mol −1.

A LEED, TPD and HREELS investigation of NO adsorption on Sn/Pt(111) surface alloys

The adsorption of NO on Pt(111), and the (2 × 2)Sn/Pt(111) and (√3 × √3)R30°Sn/Pt(111) surface alloys has been studied using LEED, TPD and HREELS. NO adsorption produces a (2 × 2) LEED pattern on Pt(111) and a (2√3 × 2√3)R30° LEED pattern on the (2 × 2)Sn/Pt(111) surface. The initial sticking coefficient of NO on the (2 × 2)Sn/Pt(111) surface alloy at 100 K is the same as that on Pt(111), S 0 = 0.9, while the initial sticking coefficient of NO on the (√3 × √3)R30°Sn/Pt(111) surface decreases to 0.6. The presence of Sn in the surface layer of Pt(111) strongly reduces the binding energy of NO in contrast to the minor effect it has on CO. The binding energy of β-state NO is reduced by 8–10 kcal/mol on the Sn/Pt(111) surface alloys compared to Pt(111). HREELS data for saturation NO coverage on both surface alloys show two vibrational frequencies at 285 and 478 cm −1 in the low frequency range and only one N-O stretching frequency at 1698 cm −1. We assign this NO species as atop, bent-bonded NO. At small NO coverage, a species with a loss at 1455 cm −1 was also observed on the (2 × 2)Sn/ Pt(111) surface alloy, similar to that observed on the Pt(111) surface. However, the atop, bent-bonded NO is the only species observed on the (√3 × √3)R30°Sn/Pt(111) surface alloy at any NO coverage studied.

Variation of the Binding Energy due to High Electrostatic Fields (NO on Rh(111))

AbstractThe influence of high electrostatic field strengths (V/nm to V/A) on the binding energy has been studied by pulsed field desorption mass spectrometry (PFDMS). For this purpose the equilibrium between adsorption and thermal desorption of NO on Rh(111) has been observed as a function of temperature and field strength. — We obtained 102.6 kJ/mol for the binding energy of NO on Rh(111) which is in good agreement with TPD measurements of Bugyi and Solymosi [1]. With a negative field strength of 3 V/nm the binding energy increases about 10%, and a decrease of about the same amount was observed for a positive field of 3 V/nm. — In an attempt to understand the effect of high field strengths on binding energy, calculations of the change in electron density due to various field strengths have been performed. These calculations were carried out within density functional theory using a nonlocal spin density approximation. The change of the electron density involved in the bonding will be shown.

Spectroscopic Study of NO (E2Σ+)-Ar Complex Using the Resonance Enhanced Multiphoton Ionization Method

The NO-Ar van der Waals complex has been generated in the molecular beam. The complex in the E2Σ+ state has been studied by using the resonance enhanced multiphoton ionization technique with a time-of-flight mass spectrometer. Two sort of excitations spectra have been measured; one is the E2Σ+-X2II excitation spectrum and the other is the E2Σ+ - A2Σ+ excitation spectrum. The 0-0 band of the complex is red-shifted by 496.8 cm-1- from that of bare NO. The binding energy of NO (E2Σ+)-Ar is determined to be 585 cm-1 and the progression due to the stretching van der Waals mode measured is extremely complex. The results are compared with those obtained for NO (A2Σ+)-Ar and NO+ (X1Σ+)-Ar complexes.

Cluster ions: Gas-phase stabilities of NO+(O2)n and NO+(CO2)n with n=1–5

Thermodynamic stabilities of cluster ions NO+(O2)n and NO+(CO2)n with n=1–5 were determined with a pulsed electron beam mass spectrometer. The measured binding energies of NO+(O2)n were found to be considerably smaller than those of NO+(N2)n, i.e., the solvating power of O2 toward NO+ is weaker than that of N2. For both NO+(O2)n and NO+(CO2)n, the cluster ions with n=3 were found to be relatively more stable toward dissociation. The experimental energies of NO+(CO2)n agree well with ab initio ones and are much larger than those of NO+(N2)n and NO+(O2)n. Structural difference between NO+(N2)n and NO+(CO2)n is also discussed. It is postulated that not NO+(O2) but NO+(CO2) is the key intermediate for conversion of NO+ to the hydronium series ions in the D region of the Earth’s atmosphere.

A TPD study of nitric oxide decomposition on Pt(100), Pt(411) and Pt(211)

Temperature programmed desorption (TPD) was used to compare nitric oxide dissociation on Pt(100), Pt(411) and Pt(211). These three faces were chosen for study because they possess sites with nearly the same orbital symmetries. However, the site densities are different on the three faces. It was found that all three faces show nearly identical reactivity for NO dissociation. Measured dissociation fractions were 66, 70 and 66% on the Pt(100), Pt(411) and Pt(211) surfaces respectively. NO dissociation on Pt(100) was inhibited by a (1 × 1) → (1 × 5) reconstruction, which creates a less active surface during the desorption process. However, the activation energy for N 2 formation was nearly identical (28 kcal mol ) on Pt(211) and Pt(411). Of course many of the features of the TPD spectra varied from face to face. Pt(100) displays a complicated TPD spectrum, due to the presence of surface reconstructions during desorption process. The binding energy of NO on the (100) steps on Pt(211) was found to be unusually strong. However, examination of the data indicates that, except for some minor effects, the variations in reactivity with changing crystal face were as expected from an examination of the symmetries of the orbitals available for reaction, and do not scale with the site density.

A TPD study of nitric oxide decomposition on Pt(100), Pt(411) and Pt(211)

Temperature programmed desorption (TPD) was used to compare nitric oxide dissociation on Pt(100), Pt(411) and Pt(211). These three faces were chosen for study because they possess sites with nearly the same orbital symmetries. However, the site densities are different on the three faces. It was found that all three faces show nearly identical reactivity for NO dissociation. Measured dissociation fractions were 66, 70 and 66% on the Pt(100), Pt(411) and Pt(211) surfaces respectively. NO dissociation on Pt(100) was inhibited by a (1 × 1) → (1 × 5) reconstruction, which creates a less active surface during the desorption process. However, the activation energy for N2 formation was nearly identical (28 kcalmol) on Pt(211) and Pt(411). Of course many of the features of the TPD spectra varied from face to face. Pt(100) displays a complicated TPD spectrum, due to the presence of surface reconstructions during desorption process. The binding energy of NO on the (100) steps on Pt(211) was found to be unusually strong. However, examination of the data indicates that, except for some minor effects, the variations in reactivity with changing crystal face were as expected from an examination of the symmetries of the orbitals available for reaction, and do not scale with the site density.